Best/simplest authentication method to validate an encrypted user/password against encrypted known-good.

[Alan DeKok]

On Apr 29, 2020, at 5:03 PM, Gleb Lisikh <in4bit.general at gmail.com> wrote:
> I'd like to be able to authenticate a user by comparing password provided
> with the client's authentication request with what's in a password store.
> It can be easily done by Clear-Text password, of course, but I cannot have
> a known good password in that password store in Clear-Text form - only
> encrypted (doesn't really matter how).

  It does matter how.  FreeRADIUS has to understand the encrypted form in order to authenticate the user.

> So ideally, i'd like to get an encrypted password string from a client, and
> compare it with an encrypted password string retrieved from the known good
> password store.

  RADIUS doesn't work that way.

  You can get the clear-text password from the user.  It's in the User-Password attribute.  You can get the encrypted password from a database such as SQL or LDAP.  The "pap" module will then compare the two.

> The retrieval of the known good password is done in the
> python module. And I'd rather not use SQL instead for the Python.

  The python module should just hand the encrypted password to FreeRADIUS, and let FreeRADIUS do the work.

  See mods-available/pap for documentation on what encrypted formats are supported.

> EAP methods encrypt the whole message using the user passwords as a key (as
> far as I understand it), which complicates the matter...

  No.  EAP methods do something rather more complex, like TLS.

  Alan DeKok.